1. Field of the Invention
The present invention relates to a zero insertion force (ZIF) socket which has a low profile and improved contacts for reliably and effectively connecting pins of a CPU to a printed circuit board on which the socket is mounted.
2. The Prior Art
ZIF sockets conveniently connect a CPU with a large number of pins to a printed circuit board without the necessity of exerting a large force to insert the CPU into the socket. The ZIF socket has a cover which is movable relative to a base, thereby displacing the pins of the CPU to engage with/disengage from contacts of the ZIF socket which are fixedly received in the base and soldered to the printed circuit board.
ZIF sockets were originally provided with actuation mechanisms (usually consisting of a lever and a cam) to displace the cover relative to the base. Such sockets are disclosed in U.S. Pat. Nos. 5,057,031 and 5,489,217.
Following the development of laptop computers which require a relatively small thickness, a low profile ZIF socket has been proposed which eliminates the actuation mechanism. A separate tool (for example, a flat screw driver) is used to actuate the cover relative to the base. Such a socket is disclosed in U.S. Pat. No. 5,730,615 ('615 patent) to Lai et al. which is assigned to the same assignee as the present application.
Although the '615 patent has proven to work well, disadvantages exist which need to be addressed.
Firstly, due to each contact 16 of the '615 patent having a substantially straight configuration, a counteractive force acting on the contact when the corresponding pin of the CPU is moved to engage therewith is resisted only by a small area of the contact, which causes the contact to be subject to a relatively high amount of stress, thus, the contact becomes easily fatigued.
Secondly, the profile of the socket in accordance with the '615 patent is still too high to meet the requirement of laptop computers which are designed to be increasingly thinner.
Hence, an improved ZIF socket is needed to eliminate the above mentioned defects of the '615 patent.